Yes, for lawyers; I can imagine doing that because it is an absolutely routine practice. If you are at all likely to be a serious client, lawyers will give you hours and hours for free. Why wouldn't they? No invoice denominated in single-digit hours is going to move the dials for them anyways.
It's more accurate to compare large ad agencies to the lawyer analogy. Which then, makes complete sense.
Back to my analogy. You will never go into a lawyers office and demand he "write a case study and strategy document" for how he plans on dealing with your crazy neighbors because they killed your dog. He will laugh you out of his office, while sending you a bill for wasting his time. But...you can walk in and ask his opinion, get a feeling for his ethics and ask for references. This is akin to the interview for the designer or developer. I see nothing wrong there, on either side.
As someone who has done pretty significant work with lawyers, especially lately: I think you're drastically underestimating how much lawyers will do up front for free.
My point in this rabbit hole is that doing "free aka spec" work for a lawyer vs designer/developer is completely different. With a lawyer you are talking about possible payouts that can equal to months, or even years of salary. For designers/developers the typical payout for spec work (for freelancers) are more like weeks.
Granted, this whole discussion around lawyers doing spec work vs designers/devs doing it is a bit convoluted. I shouldn't have used lawyer in the example, though I still don't think someone goes into a lawyers office and says "in order to work with me you must complete the following tasks". That's what happens to designers and developers, which I think it BS.